Regulating CoP\(_{x}\)/Co heterostructures for enhanced electrocatalytic activity toward hydrazine oxidation reaction

Hydrazine hydrate (N2H4∙H2O) is considered an ideal fuel for fuel cells. Constructing a cobalt phosphide/cobalt (CoPx/Co) heterostructure can achieve efficient electrocatalytic activity for hydrazine oxidation reaction. Traditional strategies for constructing CoPx/Co heterostructures took less consideration on the exposure of the active sites. In this study, 3D nanoflower-like nano CoPx/Co heterostructures with highly exposed active sites were obtained on a nickel foam (NF) through a dual-component phosphating strategy, i.e., regulating the relative content of Co and Co(OH)2 with cathodic current density and utilizing the differences in their phosphating behaviors. The potential at 100 mA∙cm‒2 and Tafel slope of the optimized CoPx/Co(375)@NF electrode prepared with the cathodic current density of 375 mA∙cm‒2 are ‒37.4 mV (vs.RHE) and 58.9 mA∙dec‒1, respectively, in a 0.2 M N2H4∙H2O solution. The stable potential was maintained after 12 h under a high current density of 100 mA∙cm‒2. The superior electrocatalysis activity toward N2H4∙H2O is proved closely relative with the constructing of CoPx/Co heterostructure. This study provides a new strategy for the development of efficient hydrazine oxidation catalysts by using a dual-component phosphating approach to fully expose the active sites of the CoPx/Co heterostructure.